Long-term presence of white spot syndrome virus (WSSV) in a cultivated shrimp population without disease outbreaks

Diseases of Aquatic Organisms

Kuan-Fu Liu¹  Meng-Feng Tsai¹  Chu-Fang Lo¹  Hwei-Chung Liu¹  Hui-Chen Hsu¹  Shao-En Peng¹  Chen-Fang Chang¹  Chung-Hsiung Wang¹  Guang-Hsiung Kou¹ 

关键词: WSSV;    Carrier brooder;    Offspring;    Virus multiplication sites;    In situ hybridization;    Penaeus monodon;   

DOI  :  10.3354/dao038107

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: PCR and in situ hybridization analysis were used for detection of white spot syndrome virus (WSSV) in an infected, cultured shrimp population over a long period in the absence of disease outbreaks. The shrimp were derived from asingle WSSV-carrier brooder and cultured first in a tank and then in outdoor ponds. Prior to harvest at 13 mo, no 1-step PCR-positive specimens were found, even though most tested specimens were found to be 2-step PCR-positive. At 7 mo, 2-stepPCR-positive tissues were found in 5 sampled shrimp. Heart, gill, integument, muscle and stomach tissues best supported viral replication. At 13 mo several shrimp died, and 1-step PCR-positive individuals were found for the first time. Althoughsuperficially healthy, 10% of the surviving adults had tiny white spots on their carapace, and in situ hybridization analysis revealed WSSV-positive cells in 40% of the specimens examined. As before, most were found in the stomach,integument and gills, and only very few in the lymphoid organ and other organs. These observations contrasted to those for experimentally infected shrimp with gross signs of terminal WSSV infection, where strong positive signals were also observed in thelymphoid organ and in other organs of ectodermal or mesodermal origin. Our results showed clearly that whatever the source, WSSV was carried in the shrimp population at a low intensity (i.e. nested PCR was required for detection) for a very long time inthe absence of massive mortality. We hypothesize that disease outbreaks do not occur if shrimp defense mechanisms manage to contain low-intensity viral infections under low-stress culture conditions. Conversely, outbreaks may occur under stressfulconditions.

【 授权许可】

Unknown